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AGXX40 KNHC 211627

Marine Weather Discussion
NWS National Hurricane Center Miami FL
1227 PM EDT Fri Jul 21 2017

Marine Weather Discussion for the Gulf of Mexico, Caribbean Sea,
and Tropical North Atlantic from 07N to 19N between 55W and 64W
and the Southwest North Atlantic including the Bahamas


Convection is increasing across much of the N half of basin late
this morning as an upper low is shifting slowly wwd across the
NE Gulf and interacting with ample llvl moisture about both sides
of lingering sfc trough. this activity expected to continue
through tonight. W Atlc ridge extends wwd along 28N and very
weakly across FL and weakly across the Gulf along about 27N, with
a sympathetic high having formed near 26N86N. 12Z obs suggested
seas 1-2 ft across entire basin except 3-4 ft across SW portions
in response to Yucatan thermal trough shifting W overnight. With
weak pres pattern to prevail across the basin next several days,
this thermal trough will dominate the Yucatan and SW gulf during
the period. A very energetic tropical wave moving across Honduras
and Nicaragua this morning will enhance Yucatan cnvtn this
afternoon through tonight and then across W Bay of Campeche and
adjacent Mexican areas through Sat night.

Otherwise, the weak ridge will dominate through Saturday
producing gentle to moderate winds and seas of 1 to 3 ft, with
the exception of the eastern Gulf, where variable winds and seas
of 2 ft or less will prevail. On Sunday, as the ridge builds
westward, expect moderate to locally fresh SE to S winds, and
seas of 3 to 5 ft across much of the W and SW Gulf through
Tuesday night, where the pressure gradient will be tighter.

55W AND 64W...

Very energetic tropical wave, former TS Don, has moved into
Nicaragua and Honduras with accompanying wind surge slowly
diminishing impacts across the W Carib waters and Gulf of
Honduras. Squalls and tstorms have moved will inland and
weakened past several hours. Seas were 6-9 ft across waters off
of Nicaragua and 5-7 ft off of Honduras at 12Z and are slowly
subsiding. This wind surge shifted area of max wind and seas from
typical location off of Colombia to this area overnight and this
morning. Meanwhile farther E, trailing strong ENE extend to S of
Hispaniola and the S Mona Passage where seas were 6-7 ft with
likely areas to 8 ft. PR buoys showing seas at 5 ft at 12Z and
down slightly from overnight. Large AEW complex covers from about
72W to the waters E through NE of the islands as secondary vort
is riding WNW up the back side of leading broad wave along 71W
and will transport this moisture across the NE Carib through
tonight. As this AEW complex moves across the remainder of basin
through the weekend, peak winds will persist across the S central
portions of the basin, in normal location where seas will
fluctuate 7-9 ft. Diurnal processes to enhance fresh E trades S
of Hispaniola through the weekend. Models show Atlc ridge
shifting slightly W by Mon and strengthening pres grad just
enough to hint at 30 kt early morning peak winds off of Colombia,
with seas to 10 ft.


High pressure ridges across the W Atlc along 28-29N to central
FL yielding moderate to fresh trades S of 23N E of Turks and
Caicos becoming SE to S winds through the Bahamas. Wind surge
associated with the broad tropical wave complex across the E and
NE Carib kicked up seas 6-7 ft with isolated spots to 8 across
the far SE waters from N of PR to N of Leewards. Elsewhere seas
relatively tranquil at 4-5 ft except # ft or less through Bahamas
and 2-3 ft across FL and GA coastal waters. TUTT low across and
just E of central Bahamas inducing increasing cnvtn attm and
looks to be an active day. Squalls and tstorm associated with
wave energy moving WNW across the waters NE of the Leewards will
shift across these waters late this afternoon through tonight.
Models in good agreement that ridge will remain generally intact
into early next week with little change to conditions, and
modified mainly by passing AEWs.


.WARNINGS...Any changes impacting coastal NWS offices will be
coordinated through AWIPS II Collaboration Chat, or by


55W AND 64W...



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